N, K = gets.split.map(&:to_i)
A = gets.split.map(&:to_i).sort

ans = A.each_index
 .each_cons(2)
 .map{|i,j| [i, j, A[i] - A[j]] }
 .sort_by(&:last)
 .take(K - 1)
 .sort_by(&:first)
 .map{|v| v[0,2] }
 .flatten
 .tap{|sec| sec.unshift(0); sec.push(N - 1)}
 .each_slice(2)
 .map{|l,r| A[r] - A[l] }
 .sum
 
puts ans